Chair

ABSTRACT

An object of this invention is to provide a chair having less sliding resistance, less abrasion and less noise with prevention of partially contacting each component while the chair is making a rocking movement. 
     The chair comprises a support frame  4  supported by a support rod  12 , a back frame  5  that can make an inclining movement relative to the support frame  4 , a seat frame  6  that is related to the support frame  4  and the back frame  5  so as to make a movement in conjunction with the back frame  5  toward a direction along the inclining movement of the back frame  5 , and a spring case  71  arranged along the seat frame  6  in a state that a proximal point part of the spring case  71  is supported by the support frame  4  so as to introduce a spring force against a force of an interlocking movement of the seat frame  6  and the back frame  5  to the support frame  4 , wherein a spring  72  is so arranged to be compressed by a movement of the seat frame  6  relative to the spring case  71 , and a slide guide part  66  to make the spring case  71  and the seat frame  6  line-contact in a direction orthogonal to the back and forth direction is arranged between the spring case  71  and the seat frame  6.

FIELD OF THE ART

This invention relates to a chair used in an office or the like, and more specifically to a chair wherein a sliding resistance between a seat frame and a spring case is reduced.

BACKGROUND ART

Conventionally, as a chair provided with a so-called synchronized rocking function wherein a seat sinks while making a sliding movement backward in conjunction with a backward inclining movement of the back, a chair has been known as shown in, for example, the patent document 1.

The chair comprises a support frame supported by a support rod, a back frame that can make a standing and inclining movement relative to the support frame, a seat frame related to the support frame and the back frame so as to make a movement in conjunction with the back frame along the standing and inclining movement of the back frame, and a spring case arranged along the seat frame in a state that a proximal point part of the spring case is supported by the seat frame so as to introduce a spring force against the coupled movement of the seat frame and the back frame to the support frame, and the spring is so arranged to compress due to a movement of the seat frame relative to the spring case.

The spring case comprises a contact surface arranged on the outside of the spring and extending in the back and forth direction, and it is so arranged that the contact surface can make a sliding movement with a corresponding contact surface that extends in the back and forth direction of the seat frame. As mentioned, if the contact area between the spring case and the seat frame is increased, it is possible to reduce the pressure applied to the seat frame and the spring case each other while the seat frame and the back frame are making a synchronized movement, resulting in enabling to reduce abrasion and noise on the contact surface.

PRIOR ART DOCUMENT Patent Document

-   Patent document 1: Japanese Unexamined Patent Application     Publication Number 2010-507399

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, if the seat frame and the spring case make a proximal contact, a sliding resistance tends to increase as a whole although the pressure between them decreases. In addition, since a direction of the back and forth movement of the seat frame is determined by a link mechanism making use of the support frame, the seat frame and the back frame, a guide such as the above-mentioned contact surface is required to form in parallel to a moving direction of the seat frame in order to reduce abrasion or noise generated by a partial contact. As a result, there is a problem that it requires a high accuracy in processing and assembling the chair.

The present claimed invention intends to solve all of the problems effectively.

Means to Solve the Problems

In order to attain this object, the following means are provided.

More specifically, the chair in accordance with this invention comprises a support frame supported by a support rod, a back frame that can make an inclining movement relative to the support frame, a seat frame that is related to the support frame and the back frame so as to make a movement in conjunction with the back frame toward a direction along the inclining movement of the back frame, and a spring case arranged along the seat frame in a state that a proximal point part is supported by the support frame so as to introduce a spring force against a force of an interlocking movement of the seat frame and the back frame to the support frame, and is so arranged that the spring is compressed by a movement of the seat frame relative to the spring case, and is characterized by that a slide guide part to make the spring case and the seat frame line-contact in a direction orthogonal to a back and forth direction or point-contact is arranged between the spring case and the seat frame.

In accordance with this arrangement, since the area of the part where the spring case makes contact with the seat frame is limited, it is possible to expect to reduce a siding resistance effectively as a whole. In addition, since the spring case and the seat frame only make a line-contact each other in the direction orthogonal to the direction of the relative movement of the spring case and the seat frame or a point-contact each other, even though the spring case is not arranged in parallel with the seat frame, it is possible for the spring case and the seat frame to contact each other so that it does not require a higher accuracy in processing and assembling the spring case and the set frame compared with a case wherein the spring case and the seat frame make a proximal contact.

Furthermore, in case that the slide guide part is so arranged that the proximal point part of the spring case is supported by the support frame rotatably around a transversal shaft and a base spring bearing is formed on an extending part locating at a distal end side of the spring case, a movable spring bearing is arranged at the seat frame side to face the base spring bearing and a spring is arranged between the base spring bearing and the movable spring bearing, it is possible to use the slide guide part more preferably.

In addition, also in case that the support frame and the spring case can be mounted and dismounted at an assembled angle at least more upright than the used angle, and a cam surface is arranged for the support frame to urge the movable spring bearing toward a direction that the spring is compressed in accordance with a movement of the spring case from the assembled angle to the used angle, it is possible to use the above-mentioned arrangement more preferably.

Furthermore, in order to make the chair compact as a whole, it is more preferable that a void part is formed on a part of the seat frame, the spring case is housed in the void part at generally the same height as that of the seat frame and a first slide guide part extending in the lateral direction is integrally formed with the seat frame at a position to press the top surface of the spring case.

In addition, even though the spring case and the seat frame are not arranged strictly in parallel, in order to keep a positional relationship between the spring case and the seat frame appropriately it is more preferable that the first slide guide part is arranged only at one position along the back and forth direction.

Furthermore, in order to support the distal end of the spring case appropriately without less resistance in the lateral direction, it is preferable that the spring case is housed between the right and left walls of the seat frame, and a second slide guide part extending in the vertical direction is arranged on either the right and left walls of the seat frame or the right and left walls of the spring case facing the right and left walls of the seat frame.

In addition, even though the spring case and the seat frame are not arranged strictly in parallel, in order to make it possible to keep a positional relationship between the spring case and the seat frame appropriately, it is more preferable that the second slide guide part is arranged only at one position along the back and forth direction.

Furthermore, in order to make it easier to incorporate the spring case into the seat frame, it is preferable that the void part opens rearward of the seat frame and the spring case can be mounted on and dismounted from the void part of the seat frame from the rearward.

In addition, in order to form the slide guide part easily and appropriately, it is preferable that the slide guide part is a projecting part whose distal end is curved to form a convex and is integrally formed with the spring case or the seat frame.

Effect of the Invention

In accordance with the above-mentioned presently claimed invention, it is possible to provide a chair that can reduce a sliding resistance due to a synchronized movement between the seat frame and the spring case without requiring high accuracy in processing and assembling the chair.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a chair in accordance with one embodiment of this invention.

FIG. 2 is an exploded perspective view of the chair.

FIG. 3 is the perspective view of a principal part to explain a link mechanism between frames of the chair.

FIG. 4 is a perspective view of a support frame constituting the chair.

FIG. 5 is a perspective view, cut by a center line of a longitudinal direction, of a seat frame constituting the chair.

FIG. 6 is an exploded perspective view of a reactive force mechanism and a lock mechanism of the chair.

FIG. 7 is a cross sectional perspective view of the reactive force mechanism of the chair.

FIG. 8 is a cross sectional perspective view of the reactive force mechanism at a time when a back frame of the chair inclines rearward.

FIGS. 9 (a) through (c) are cross section views to explain a behavior of the reactive force mechanism at a time when the seat frame and the reactive force mechanism engage the support frame and the back frame of the chair.

FIG. 10 is a perspective view of a principal part showing an assembled state of a stopper mechanism of the chair.

FIG. 11 is a perspective view of a principal part showing a disassembled state of the stopper mechanism of the chair.

FIGS. 12 (a) through (c) are cross sectional views showing a positional relationship among a stopper member, a stopper case, a spring case and a movable plate of the seat frame.

FIGS. 13 (a) through (g) are cross sectional views of a principal part to explain a mechanism of a behavior of a rocking stopper of the chair.

FIG. 14 is a perspective view of a principal part to explain a seat height adjusting mechanism of the chair.

FIG. 15 is a cross sectional view of a principal part to explain a method for assembling the seat height adjusting mechanism of the chair.

FIG. 16 is a cross sectional view of a principal part in a state a gas spring lever is incorporated into the support frame of the chair.

FIG. 17 is a perspective view of a principal part in a state prior to incorporation of the gas spring lever into the support frame of the chair.

FIGS. 18 (a) and (b) are perspective views of a principal part to explain a behavior of a reactive force adjusting part of the chair.

FIGS. 19 (a) through (d) are cross sectional views of a principal part to explain a bearing area of each engaging part of the chair.

FIG. 20 is a perspective view of a principal part to show an engaged state of the bearing member and a slide bore with a front transversal shaft of the chair.

FIG. 21 is a cross sectional view of a principal part at a time when the gas spring lever of the chair is operated.

FIG. 22 is a pattern diagram to explain an angle of inserting and dismounting the gas spring lever of the chair.

FIGS. 23 (a) through (c) are perspective views of a principal part of the seat frame constituting a chair in accordance with another embodiment of this invention.

BEST MODES OF EMBODYING THE INVENTION

One embodiment of this invention will be described with reference drawings.

A chair of this embodiment is, as shown in FIG. 1 and FIG. 2, a swivel chair wherein a chair body 3 is rotatably mounted on a leg blade 11 through a support rod 12, and comprises a support frame 4, a back frame and a seat frame 6 supported by the support rod 12, and forms a link mechanism by engaging the support frame 4, the back frame 5 and the seat frame 6 each other as shown in FIG. 3.

In the specification of this invention, a direction from a center of the chair to a back 31 is set as a rear direction, and the opposite direction is set as a front direction. In other words, the left side in FIG. 1 is the front direction, and the right side in FIG. 1 is the rear direction. In addition, a vertical direction is called as an up and down direction, and a direction orthogonal to a back and forth direction and the vertical direction is called as a lateral direction or a right and left direction.

The support frame 4 is, as shown in FIG. 4, integrally formed of a material such as an aluminum die-casting or a resin, and mainly comprises a boat-shaped main frame 41 having a right wall 411, a left wall 411, a rear wall 412, a front wall 413 and a bottom wall 414 and at least a boss bore 42 as being a mounting bore to mount the support rod 12 on the main frame 41, a transversal rib 415 connecting the right side wall 411 and the left side wall 411, a longitudinal rib 416 to connect the front wall 413, the rear wall 412 and a transversal rib 415, and a diagonal rib 417 to support the boss bore 42 on the main frame 41 are integrally formed with the main frame 41. In addition, a gas spring lever mounting part 43 comprising a mounting bore 431 to mount the gas spring lever, to be described later, is arranged in a top part near the boss bore 42. A front transversal shaft 44, with which a projecting part projecting right and left is integrally connected, is integrally formed on the top part of the front wall 413 of the main frame 41. The front transversal shaft 44 is divided into three areas based on the function, and the area projecting right and left from the main frame 41 is set as an engaging part 441 as being a second transversal shaft to engage the seat frame 6, and the area formed inside of the main frame 41 is set as an engaging part 442 as being a forth transversal shaft to engage a spring case 71, to be described later, and each of the areas is arranged to be coaxial. A rear transversal shaft 45 as being a first transversal shaft projecting right and left is integrally formed on the right and left side walls 411, 411 of the main frame 41.

The back frame 5 is, as shown in FIG. 2, integrally formed of a material such as an aluminum die-casting or a resin, and a middle part of a pair of right and left frame members 51 is connected by a middle transversal shaft 52 as being a projecting part as a third transversal shaft, and a frontward facing opening concave part 53 having a cylindrical shape from which a part is cut is formed on a bottom end part of the back frame 5. A moderate mountain-shaped prominent part 511 is integrally formed with the frame member 51, and the middle transversal shaft 52 is arranged at positions connecting an inner surface of the right prominent part 511 and an inner surface of the left prominent part 511.

The seat frame 6 is, as shown in FIG. 5 and FIG. 6, integrally formed of a resin material, and is formed into a shape wherein a pair of right and left main frames 61 extending back and forth are connected by a front wall 611 and a bottom wall 616, and the main frame 61 is formed in a shape wherein an inside wall 612 and an outside wall 613, each of which is in a plate shape, are connected by a transversal rib 614. And a void part 65 to incorporate a spring case 71, to be described later, is arranged on a top side of the seat frame 6 and its rearward is formed as an opening end 69 and a top lid 615 is arranged at a position across the front of the inside wall 612 and the front wall 611. Furthermore, the bottom wall 616 and the inside wall 612 extend to reach around the bottom of the top lid 615, and a space 63 for connection is formed below the top lid 615, and a rotation slide bore 62 whose side view is an elongated bore is formed on the inside wall 612 to open downward in a state that a part is cut.

The seat frame 6 of this embodiment comprises the void part 65 as mentioned above, however, it is not necessarily the case that the void part 65 is in a shape of opening upward, and may be in a shape of closing upward or opening downward.

In addition, the inside wall 612 and the outside wall 613 of the seat frame 6 extend further rearward from the bottom wall 616, and a downward facing opening concave part 64 in a shape of a cylinder from which a part is cut is formed on the downward of the extending part. An innermost recess of the downward facing opening concave part 64 is a bearing surface along a partial cylindrical surface, and its opening end faces front downward.

As shown in FIG. 4, FIG. 5 and FIG. 7, the front transversal shaft 44 and the rotation slide bore 62 form a rotation slide engaging part 91 by inserting the front wall 413 of the support frame 4 into the space 63 for connection of the seat frame 6 and engaging the seat frame engaging part 441 arranged near both end parts of the front transversal shaft 44 above the front wall 413 with the rotation slide bore 62 arranged on the right and left inside walls 612 of the seat frame 6. An engaging part 92 of the back frame 5 and the support frame 4 and an engaging part 93 of the seat frame 6 and the back frame 5 are formed as shown in FIG. 3, FIG. 7 and FIG. 8 by engaging the frontward facing opening concave part 53 of the back frame 5 with the rear transversal shaft 45 of the support frame 4 in a state of being able to make an inclining movement, and further by engaging the downward facing opening concave part 64 of the seat frame 6 with the middle transversal shaft 52 of the back frame 5 as shown in FIG. 3. Then it is possible to realize a synchronized rocking movement to move the backside of the seat frame 6 rearward while sinking in conjunction with the rearward inclining movement of the back frame 5 and to move the backside of the seat frame 6 forward while lifting up in conjunction with the movement of the back frame 5 to stand upright.

In addition, a reactive force mechanism 7 is formed so as to accumulate a spring force against an interlocking movement of the seat frame 6 and the back frame 5 to the support frame 4.

The reactive force mechanism 7 is so arranged, as shown in FIG. 6, FIG. 7 and FIG. 8, a spring 72 and a movable spring bearing 73 are housed in the spring case 71 that opens downward as being a spring support part in this invention, and the spring 72 is compressed by changing a position of the movable spring bearing 73 with a sliding movement of the seat frame 6 relative to the spring case 71 in accordance with a rearward inclining movement of the back frame 5 by engaging the spring case 71 with the front transversal shaft 44 of the support frame 4.

As its detail is described later, a front end part of the spring case 71 makes an engagement with the support frame 4 and the spring case 71 is restricted from moving in a vertical direction and a lateral direction by the seat frame 6, and furthermore a rear end part of the spring case 71 is also restricted from moving in the vertical direction and the lateral direction by the seat frame 6 with forming a lock mechanism 8, to be described later. As a result, the spring case 71 makes a vertical movement integrally with the seat frame 6 and only a movement in the back and forth direction relative to the seat frame 6 is allowed to make for the spring case 71.

Concrete structure will be described.

The spring case 71 is, as shown in FIG. 6 and FIG. 7, made of a steel material formed into a cuboid opening downward and comprising a top wall 711, right and left side walls 712 and a rear wall 713, and a movable plate part 714 as being a rear end part of the spring case 71 elongates from a bottom part of the rear wall 713 toward a rear direction orthogonal to the rear wall 713. In addition, the spring case 71 has an arrangement that a bearing member 74, which has a convex part 741 corresponding to a base point part 716 and which forms a downward facing opening concave part 742 by a partial cylindrical surface to be a bearing surface, is mounted on the base point part 716 comprising a concave part set in a front end side of the top wall 711, and a portion near a center of the rear wall 713, which locates rear of the base point part 716, is set as a base spring bearing 75. A through bore 751 is arranged on the base spring bearing 75.

The spring case 71 is restricted from moving upward by making an engagement with the support frame 4 through the bearing member 74 at the base point part 716 of the front end part of the spring case 71 and by placing the top lid 615 of the seat frame 6 on top of the top wall 711. In addition, near the front end part of the spring case 71, the right and left side walls 712 are restricted from making a relative movement in the right and left directions by the inside wall 612 of the seat frame 6. Since the rotation slide engaging part 91 is formed by engaging the rotation slide bore 62 of the seat frame 6 with the front transversal shaft 44 of the support frame 4, the seat frame 6 is restricted from making a vertical movement at this point by the support frame 4. As a result, the front end part of the spring case 71 is restricted from making a vertical movement by being sandwiched between the top lid 615 of the seat frame 6 and the front transversal shaft 44 of the support frame 4. With this arrangement, the front end part of the spring case 71 is restricted from making a movement in a direction except for the back and forth direction relative to the seat frame 6.

Furthermore, with the arrangement that the movable plate part 714 as being the rear end part of the spring case 71 forms a lock mechanism, to be described later, together with the seat frame 6, the movable plate part 714 is restricted from making a movement vertically and laterally relative to the seat frame 6. As a result of this, it is possible for the spring case 71 as a whole to make only a movement in the back and forth direction relative to the seat frame 6.

The spring case 71 can be inserted into or dismounted from the opening end 69 locating at a rear side of the void part 65 of the seat frame 6, and is in the same height as that of the seat frame 6 in a state that the spring case 71 is housed in the void part 65 of the seat frame 6 and the right and left side walls 712 of the spring case 71 are housed between the right and left inside walls 612 of the seat frame 6. While the bearing member 74 forms an engaging part 94, as shown in FIG. 20, by making an engagement with the front transversal shaft 44 of the support frame 4 rotatably in a hooked state, the seat frame 6 moves relative to the spring case 71 because the seat frame 6 makes a sliding movement back and forth with the rotation slide engaging part 91 as mentioned. Since the spring case 71 rotates from an assembled position shown in FIG. 9( a) to a used position shown in FIG. 9( c) through a process shown in FIG. 9( b) with compressing the spring 72, the reactive force of the spring 72 acts in a direction to return the spring case 71 to the assembled position. In addition, the spring case 71 is restricted from making a movement relative to the seat frame 6 except for the back and forth direction. As a means to restrict the movement, for example, as shown in FIG. 5, a first slide guide part 66 and a second slide guide part 67 to allow the spring case 71 and the seat frame 6 to make a sliding movement smoothly are arranged at a position where the spring case 71 makes an abutting contact with the seat frame 6.

The first slide guide part 66 is a projecting part that is integrally formed on a top edge of the inside wall 612 of the seat frame 6 and that extends in parallel to the bottom wall 616 of the seat frame 6, and the projecting part is curved to form a gentle convex. In a state that the spring case 71 is incorporated into the seat frame 6 as shown in FIG. 7, the projecting part 66 makes a line contact with the top surface of the spring case 71 in the transversal direction orthogonal to the back and forth direction so as to push the spring case 71 downward. In addition, as shown in FIG. 5, the second slide guide part 67 is a projecting part that is integrally formed on the right and left side walls 612 of the seat frame 6 and that extends in the vertical direction, and the projecting part 67 is curved to form a gentle convex toward the inward, and the projecting part 67 makes a line contact with the right and left side walls 712 of the spring case 71 shown in FIG. 6 in a vertical direction orthogonal to the back and forth direction so as to prevent the spring case 71 from swinging in the right and left directions. In order to facilitate setting the reference position of the spring case 71 and manufacturing the seat frame 6, the first slide guide part 66 and the second slide guide part 67 are arranged at the same position in the back and forth direction in this embodiment.

In addition, as shown in FIG. 5, a third slide guide part 68 is supplementarily arranged at a position, which is different in the back and forth direction from the position of the first slide guide part 66, in the rear of the seat frame 6. The third slide guide part 68 is a projecting part that is integrally formed on an inside of the bottom wall 616 of the seat frame 6 in a curved shape to form a gentle convex. The third slide guide part 68 is arranged at a position to make a sliding movement on the bottom surface of a movable plate part 714 of the spring case 71 incorporated as shown in FIG. 6 and FIG. 7 and can make a line contact with the bottom surface of the movable plate part 714 of the spring case 71 in a transversal direction orthogonal to the back and forth direction. With this arrangement, there is no need of especially high accuracy for the bottom wall 616 except for the third slide guide part 68 so that it becomes easier to process the seat frame 6.

As shown in FIG. 5, each of the first slide guide part 66, the second slide guide part 67, and the third slide guide part 68 is arranged only at one portion along a back and forth direction respectively.

As shown in FIG. 6 and FIG. 7, the spring 72 of the reactive force mechanism 7 is a spiral compression coil spring.

The movable spring bearing 73 is a spring bearing extension arm 731 integrally extending from a spring abutting surface 733, and the movable spring bearing 73 faces the base spring bearing 75 in a state wherein a distal end 734 of the spring bearing extension arm 731 passes inside of the spring 72 and then is inserted into a through bore 751 of the base spring bearing 75. The spring abutting surface 733 is a part of a channel-shaped displacement transmission member 732 and plays a role to transmit a slide displacement of the seat frame 6 in accordance with a backward inclining movement of the back frame 5 to the spring 72 through a reactive force adjusting part 76. The reactive force adjusting part 76 transforms, as shown in FIG. 18, a movement in the lateral direction of an adjusting amount input member 761 to a movement in the back and forth direction of an adjusting amount output member 762 by making an inclined surface 767 of the adjusting amount input member 761 and an inclined surface 768 of the adjusting amount output member 762 abutting contact, and changes a position of the displacement transmission member 732, namely a position of the spring abutting surface 733 to a direction toward which the spring 72 shown in FIG. 7 compresses or to its opposite direction. The adjusting amount input member 761 shown in FIG. 6 and FIG. 18 moves back and forth, as shown in FIG. 5 and FIG. 7, by following a back and forth movement of the seat frame 6 in a state that a part of the adjusting amount input member 761 makes an engagement with an upright part 617 arranged on the bottom wall 616 of the seat frame 6 in a slidable manner in a direction orthogonal to the back and forth direction. As shown in FIG. 18( a) and (b), it is possible for the adjusting amount input member 761 to feed screw by threadably mounting the reactive force adjusting lever 764 on a screw hole 763 arranged on the adjusting amount input member 761 and by operating a grip part 765 arranged on the outside end of the adjusting amount input member 761. In addition, as shown in FIG. 3 and FIG. 6, a part of the adjusting amount input member 761 is mounted on an appropriate position of the seat frame 6 rotatably and in a state that a flange part 766 arranged on the axis engages a part of the seat frame 6 so as not to move in the axial direction. Since the reactive force adjusting lever 764 moves back and forth integrally with the seat frame 6, a position relative to a person who is seated is kept constant.

A procedure to assemble the support frame 4, the seat frame 6, the back frame 5 and the spring case 71 will be explained by the use of FIG. 9.

The bearing member 74 of the spring case 71 is mountable on and dismountable from a direction crossing to the front transversal shaft 44 of the support frame 4 at an assembled angle at least more upright than a used angle as shown in FIG. 9( a) due to a shape of the downward facing opening concave part 742 of the bearing member 74 of the spring case 71. Similar to this, the rotation slide bore 62 of the seat frame 6 is also mountable on and dismountable from a direction crossing to the front transversal shaft 44 of the support frame 4 at the above-mentioned assembled angle through an opening in a state that the reactive force mechanism 7 including the spring case 71 is housed inside of the seat frame 6. As a result, first the reactive force mechanism 7 including the spring case 71 is incorporated into the seat frame 6 and then the spring case 71 and the seat frame 6 are engaged with the front transversal shaft 44 of the support frame 4 simultaneously at a predetermined assemble angle.

As shown in FIG. 9( b), FIG. 9( c), the seat frame 6 is integrally rotatable with the reactive force mechanism 7 from the assembled angle toward the used angle in a state that the seat frame 6 is engaged with the front transversal shaft 44 together with the spring case 71. In this case, a cam surface 46 that urges the movable spring bearing 73 toward the spring compressed direction in accordance with a movement of the spring case 71 from the assembled angle to the used angle is arranged on the support frame 4. The cam surface 46 extends from the front transversal shaft 44 to the rear downward direction generally along a tangent line and its direction is changed downward through a round part, and makes a sliding movement with a front surface of the upright part 617 arranged in front of the bottom wall 616 of the seat frame 6 as shown in FIG. 5. With this arrangement, as shown in FIG. 9( a), (b) and (c), while the spring case 71 rotates with a center on the front transversal shaft 44 on the bearing member 74, the seat frame 4 makes a sliding movement rearward with the front transversal shaft 44 floating inside of the rotation slide bore 62 and an initial reactive force is accumulated during this period. The cam surface 46 also serves as a role of a rib to reinforce the front transversal shaft 44 as shown in FIG. 4.

As shown in FIG. 9( a), (b) and (c), engageable and disengabeable parts (engaging parts) 92, 91, 93, 94 as shown in FIG. 7 are formed between the support frame 4 and the back frame 5, between the support frame 4 and the seat frame 6, between the seat frame 6 and the back frame 5 and between the support frame 4 and the seat frame 6 by engaging the front facing opening concave part 53 of the back frame 5 with the rear transversal shaft 45 of the support frame 4 from an orthogonal direction and by hooking the downward facing opening concave part 64 of the seat frame 6 at the middle transversal shaft 52 of the back frame 5. Each of these engaging parts 91, 94, 93, and 92 comprises a combination of the shaft and the concave part shown in FIG. 19( a), (b), (c) and (d). Since each of shaded parts 951, 961, 952, 962, 953, 963, 954, 964 in FIG. 19( a), (b), (c) and (d) makes a sliding movement respectively, these portions are processed to have a smooth surface as the bearing area.

Since the initial reactive force of the spring 72 in a state shown in FIG. 7 and FIG. 9( c) acts to draw the middle transversal shaft 52 of the back frame 5 to a direction of the front transversal shaft 44 of the support frame 4 through the downward facing opening concave part 64 of the seat frame 6, the initial reactive force acts to strengthen engagement of the seat frame 6 and the back frame 5 and to strengthen engagement of the back frame 5 and the support frame 4 by pushing the front facing opening concave part 53 of the back frame 5 against the rear transversal shaft 45 of the support frame 4, and further to strengthen engagement of the bearing member 74 of the spring case 71 incorporated into the seat frame 6 and the front transversal shaft 44 of the support frame 4. As a result, these engaging parts keep the mutual engaged state by making use of the initial reactive force of the reactive force mechanism 7. Furthermore, as shown FIG. 7→FIG. 8, a reactive force that exceeds the initial reactive force of the reactive force mechanism 7 is generated in conjunction with a movement of the back frame 5 and the seat frame 6 so as to strengthen the force acting in a direction to strengthen the engagement of the seat frame 6 and the back frame 5, the engagement of the back frame 5 and the support frame 4, the engagement of the support frame 4 and the seat frame 6 respectively.

Especially, as shown in FIG. 7, FIG. 8 and FIG. 19, while the backrest makes a rocking movement between the upright position and the rearward inclining position, the bearing member 74 makes a sliding movement on a predetermined bearing area 952 of the front transversal shaft 44 in a state that the bearing member 74 is hooked at the spring case engaging part 442 near the center part of the front transversal shaft 44, and the rotation engaging bore 618 of the seat frame 6 makes a sliding movement on a predetermined bearing area 951 of the seat frame engaging part 441 near both end parts of the front transversal shaft 44. Furthermore, the front facing opening concave part 53 of the back frame 5 having a positional relation shown in FIG. 9 makes a sliding movement on the bearing area 954, to which a fitting force is especially applied, of the rear transversal shaft 45 in a state that the front facing opening concave part 53 is engaged with the rear transversal shaft 45 of the support frame 4, and the downward facing opening concave part 64 of the seat frame 6 makes a sliding movement on the bearing area 953, along a surface to which a fitting force is especially applied, of the middle transversal shaft 52 in a state that the downward facing opening concave part 64 is engaged with the middle transversal shaft 52 of the back frame 5. At least the bearing areas of these transversal shafts 44, 45, 52 constitute smooth convex sliding surfaces around the transversal axial lines (m) as being right and left axial lines each of which is parallel and passing a center of each transversal shaft 44, 45, 52 illustrated in FIG. 4 as an example. In addition, opening concave part 742, 618, 53, 64 also constitute smooth convex sliding surfaces around the transversal axial lines (m) each of which is parallel. The rotation slide bore 62 also constitutes the sliding surface.

Especially, as shown in FIG. 4 and FIG. 2, a circumferential groove 451 is arranged on a part of an outer circumferential surface of the rear transversal shaft 45 as being the projecting part of the support frame 4, and a recess 452 is arranged as a deformed part along a circumferential direction on a groove bottom of the circumferential groove 451 as being an outer circumference of the projecting part, and the outer circumferential surface other than the recess 452 is an intermittent convex sliding surface 453. A cover part 54 is integrally arranged on a side of the front facing opening concave part 53 of the back frame 5 to be fit over the convex sliding surface 453 to cover a projecting end surface 454 of the rear transversal shaft 45 at a time when the cover part 54 engages the rear transversal shaft 45 as being the projecting part of the support frame 4 shown in FIG. 4. The recess 452 can be used as a grease pool, if used as the grease pool, it is possible to reduce a sliding resistance. In addition, it is possible to form a flange-shaped big diameter part as a deformed part on each of the transversal shaft 44, 45, 52 as being the projecting part and to prevent displacement in axial direction of each opening concave part 742, 618, 53, 64 to be fitted into. Furthermore, a deformed part having a shape convenient for assembling may be arranged on a part of each transversal shaft 44, 45, 52 unless a relative movement to each opening concave part 742, 618, 53, 64 is not prevented.

Furthermore, this embodiment is provided with a lock mechanism 8, as shown in FIG. 10 and FIG. 11, that locks a rocking movement, as shown in FIG. 7 and FIG. 8, of the back frame 5 and the seat frame 6 at a predetermined position.

The lock mechanism 8 comprises a stopper case 81 mounted inside of the seat frame 6, a stopper member 82 having a plate shape housed in the stopper case 81, a movable plate part 714 having an engaging bore 715 that is arranged in the rearward of the spring case 71 and into which the stopper member 82 is inserted, and a reciprocatory moving mechanism 85 that reciprocates the stopper member 82 vertically. With the arrangement of the lock mechanism 8, since the movable plate part 714 as being a rear end part of the spring case 71 is inserted between the stopper case 81 and the seat frame 6, the movable plate part 714 is restricted from making a vertical movement. In addition, as mentioned above, the right and left side walls 712 of the spring case 71 is housed between the right and left inside walls 612 of the seat frame 6, and the spring case 71 is restricted from making a relative movement also in the right and left directions by the second slide guide part 67 near the rear end part of the spring case 71. As a result, the rear end part of the spring case 71 is incapable of making a movement both vertically and right and left relative to the seat frame 6, and is allowed to make a movement in the back and forth directions only. The movement of the spring case 71 in the back and forth directions can be fixed at a predetermined position by the behavior of the lock mechanism 8.

The reciprocatory moving mechanism 85 comprises a torsion coil spring 83 to give a vertical operational force to the stopper member 82 and an operation lever 84. The stopper member 82 is integrally made of a steel or resin material into a plate shape having two rectangular projecting parts 821 on its bottom part, and is provided with an insertion bore 822 near its top part to mount an end part 831 of the torsion coil spring 83. The stopper case 81 is made of a steel or resin material integrally formed or by a folding process into a channel shape comprising three flat surfaces, namely a front wall 811 and a rear wall 812 as being a pair of facing walls connected by a bottom wall 813 as being a fixing plate part, and a slit-shaped engaging bore 814 having almost the same shape as that of the projecting part 821 locating on the bottom part of the stopper member 82 opens on the bottom wall 813 as shown in FIG. 12.

In addition, the engaging bore 715 on the movable plate part 714 locating at the rear side of the spring case 71 is also a slit having almost the same shape as that of the projecting part 821 locating on the bottom part of the stopper member 82, and a plurality of engaging bores 715 are arranged at a predetermined pitch in the back and forth direction. The slit-shaped engaging bore 618 having almost the same as that of the projecting part 821 is arranged at a position corresponding to the projecting part 821 of the stopper member 82.

As shown in FIG. 10 and FIG. 11, the operation lever 84 is formed into a stick shape whose cross section is a general rectangle, and an operation end 841 to be operated by a person is formed into a flat shape and an insertion bore 843 to insert an end part 831 of the torsion coil spring 83 is arranged on a side surface at a working end 842 side to move the stopper member 82 vertically and a recess part 845 formed by cutting a part is arranged to house the torsion coil spring 83. In addition, a pair of mounting shafts 844 to mount the operation lever 84 on the seat frame 6 are arranged between the operation end 841 and the working end 842 in a direction orthogonal to a longitudinal direction of the operation lever 84.

The stopper case 81 is fixed near a rear side of the seat frame 6, the stopper member 82 is arranged inside of the stopper case 81 in a state of being able to make a vertical movement while being guided by one surface of the stopper member 82 that makes an abutting contact with the front wall 811, and the working end 842 of the operation lever 84 to operate the stopper member 82 is inserted into the stopper case 81 from its lateral direction so that the stopper member 82 and the working end 842 of the operation lever 84 is tightly arranged in the stopper case 81. A reason why one surface of the stopper member 82 makes an abutting contact with the front wall 811 of the stopper case 81 is to stabilize a position of the stopper member 82 by making use of the front wall 811 as a guide together with the working end 842 tightly arranged. The stopper member 82 may be arranged to make an abutting contact with the rear wall 812 of the stopper case 81. With this arrangement, the same effect can be obtained.

In addition, the torsion coil spring 83 is mounted between the stopper member 82 and the operation lever 84 to be housed in the recess part 845 arranged near the working end 842 of the operation lever 84, and two spring ends 831 each projecting opposite direction each other in a direction orthogonal to the coil direction of the spring are inserted into the insertion bore 822 of the stopper member 82 and the insertion bore 843 of the operation lever 84 respectively. Furthermore, the operation end 841 of the operation lever 84 passes the lever insertion bore 691 arranged on the side wall of the seat frame 6 so as to extend to a position accessible for a person, and the mounting shaft 844 makes an engagement in a rotatable manner with the lever mounting part 692 that grips the mounting shaft 844 and that is arranged on the outer surface of the outside wall 613 of the seat frame 6.

With this arrangement, the working end 842 of the operation lever 84 makes a vertical movement inside of the stopper case 81 by operating the operation end 841 of the operation lever 84 vertically. This movement drives the stopper member 82 to make a vertical movement through the torsion coil spring 83 so that the stopper member 82 makes an abutting contact with the front wall 811 of the stopper case 81 and makes a vertical movement in a state of being guided by the front wall 811 and the projecting part 821 of the stopper member 82 makes a movement of being inserted into or taken out from an engaging bore 815 arranged on the bottom wall 813 of the stopper case 81.

Then a relative movement of the frame 6 and the spring case 71 is restricted and a rocking movement is locked at a time when the projecting part 821 of the stopper member 82 projects downward from the engaging bore 815 of the stopper case 81 and then the projecting part 821 is inserted into a slit-shaped engaging bore 715 that locates below the engaging bore 815 and that is arranged on the movable plate part 714 of the spring case 71.

Concretely, each part acts as follows and then rocking movement is locked.

As shown in FIG. 12( a), in case that the operation lever 84 is operated so that the spring force acts on the stopper member 82 locating upside to move downward, the projecting part 821 of the stopper member 82 protrudes from the engaging bore 814 arranged on the bottom wall 813 of the stopper case 81 and then makes contact with the spring case 71 locating on the downside. At this time, in case that the slit-shaped engaging bore 715 arranged on the movable plate part 714 of the spring case 71 locates at a position corresponding to the engaging bore 814, the projecting part 821 of the stopper member 82 is inserted into the slit-shaped engaging bore 715 as shown in FIG. 12 (b). Even though a case that the slit-shaped engaging bore 715 arranged on the movable plate part 714 does not locate at a position corresponding to the projecting part 821 of the stopper member 82, if a relative position of the seat frame 6 and the spring case 71 changes by changing a gradient of the back frame 5 as shown in FIG. 7 and FIG. 8, so that the engaging bore 715 of the movable plate part 714 coincides with a position corresponding to the stopper member 82 as shown in FIG. 12 (b) or FIG. 12 (c), the projecting part 821 of the stopper member 82 is inserted. Furthermore, the stopper member 82 is simultaneously inserted into the slit-shaped engaging bore 618 of the bottom wall 616 of the seat frame 6.

The rocking position is locked because the relative movement between the seat frame 6 and the spring case 71 is restricted by restricting the projecting part 821 of the stopper member 82 that is restricted from moving back and forth to the seat frame 6 through the stopper case 81 is fittingly inserted into the slit-shaped engaging bore 715 of the movable plate part 714 of the spring case 71. At this time, if each size of the projecting part 821 of the stopper member 82 and the engaging bore 715 of the movable plate part 714 is set so as to be tightly fit each other in the back and forth direction, it is possible to lessen positional misalignment of the stopper member 82 and the movable plate part 714 after locked. Furthermore, in this embodiment, since the stopper member 82 is also inserted into the slit-shaped engaging bore 618 of the bottom wall 616 of the seat frame 6 simultaneously and a sharing force applied to the stopper member 82 concentrates only on the projecting part 821 locating at a distal end of the stopper member 82, it is possible to prevent deformation of the stopper member 82.

In addition, as mentioned, since the movable plate part 714 as being the rear end part of the spring case 71 is restricted from making a vertical movement relative to the seat frame 6 and the engaging bore 715 of the movable plate part 714 locates at a position vertically near the slit-shaped engaging bore 618 of the bottom wall 616 of the seat frame 6 on a constant basis, the positional misalignment is difficult to generate and it becomes easy to fittingly insert the stopper member 82 into the engaging bore 715 and the slit-shaped engaging bore 618 simultaneously. Furthermore, the movable plate part 714 as being the rear end part of the spring case 71 is restricted from making a movement also in the right and left directions relative to the seat frame 6, it is easy for the engaging bore 715 of the movable plate part 714 to keep in parallel with the slit-shaped engaging bore 618 of the seat frame 6 so that it becomes easier to insert the stopper member 82. As a result of this, it is possible to improve operationality of the stopper member 82 and also possible to lessen clearance by diminishing a dimensional difference between the projecting part 821 of the stopper member 82 and the engaging bore 715 and the slit-shaped engaging bore 618.

At a time of releasing a locked state, the operation lever 84 shown in FIG. 10 is operated to raise the stopper member 82 as shown in FIG. 12 (a) so as to lift up the projecting part 821 from the engaging bore 618 of the seat frame 6 and the engaging bore 715 of the spring case 71. With this operation, restriction of the relative movement between the seat frame 6 and the spring case 71 is released, which makes it possible to make a rocking movement again. With this operation, it becomes possible to change the rocking position also to a desired position as shown in FIG. 12 (b), and (c).

In addition, in this embodiment, as shown in FIG. 11 and FIG. 13, the operation lever 84 and the stopper member 82 is connected by the torsion coil spring 83 and it is so arranged that an upward force and a downward force can be applied to the stopper member 82 only by a single spring member.

Specifically, as shown in FIG. 11 and FIG. 13, a positional relationship between the insertion bore 843 for the end part 831 of the torsion coil spring 83 arranged near the working end 842 of the operation lever 84 and the insertion bore 822 for the end part 831 of the torsion coil spring 83 arranged on the stopper member 82 is shifted in right or left direction. In case that both end parts 831, 831 of the torsion coil spring 83 are mounted on the insertion bore 843 and the insertion bore 822 respectively, it is so arranged that a force to extend and open the torsion coil spring 83 is applied to both end parts 831, 831 of the torsion coil spring 83 on a constant basis. Since the torsion coil spring 83 is supported by each insertion bore 843, 822 in a state of being able to make a rotational movement, the torsion coil spring 83 is arranged to change its direction automatically in the most balanced position due to the positional relationship between both of the insertion bores 843, 822.

Concretely, an operation will be conducted as follows.

First, as shown in the left view of FIG. 13 (a), in a state that the operation lever 84 is located at the unlock position so that its working end 842 locates downside and the stopper member 82 is lifted upward, the torsion coil spring 83 locates at the right side in FIG. 13 (a) of the insertion bores 843, 822 and at a higher position than the working end 842 of the operation lever 84. In this positional relationship, the force to extend and open the torsion coil spring 83 gives the working end 842 of the operation lever 84 a force to move further downward and the stopper member 82 to move further upward respectively so that the current state can be furthermore stabilized. In case that the operation lever 84 is changed to the lock position, the positional relationship goes through the process of the left view in FIG. 13 (b), the left view in FIG. 13 (c) and the left view in FIG. 13 (d) and ends up with the positional relationship shown in the left view in FIG. 13 (e) wherein the working end 842 of the operation lever 84 locates downside and the stopper member 82 moves downward. During a process of the movement, the torsion coil spring 83 moves leftward as shown in the right view in FIG. 13 (b), the right view in FIG. 13 (c), the right view in FIG. 13 (d) and the right view in FIG. 13 (e). Contrary to the unlocked position, the force to extend and open the torsion coil spring 83 gives the working end 842 of the operation lever 84 a force to move further upward and the stopper member 82 to move further downward respectively so that the stabilized state can be kept. In case that the operation lever 84 is again changed to the unlock position from the above-mentioned state, the state is returned to the state in FIG. 13 (g), namely the same state as shown in FIG. 13 (a) through a process shown in FIG. 13 (f).

In addition, as shown in FIG. 2 and FIG. 14, the height adjusting mechanism 2 to adjust a height of the seat surface 32 is incorporated into the chair of this embodiment, and the height adjusting mechanism 2 comprises a gas spring 21 generally incorporated into the support rod 12 and a gas spring lever 22 to push a projecting and sinking member 211 locating above the gas spring 21. A working end 222 is moved downward by making use of the engaging part 223 as a fulcrum by pulling up the operating end 221 of the gas spring lever 22 and the height of the seat surface 32 can be adjusted through the support frame 4 by pushing the projecting and sinking member 211 of the gas spring 21.

As shown in FIG. 14 and FIG. 15, the support rod 12 into which the gas spring 21 is incorporated is in a shape of a general cylinder comprising a convex part 212 on a part of the support rod 12 in its axial direction, and its lower end is fittingly inserted into a top part of the leg blade 11. The boss bore 42 as being a support rod mounting bore of the support frame 4 fits together by insertion on a top end of the support rod 12 and the convex part 121 receives the weight and rotatably supports the support frame 4. At this time, the projecting and sinking member 211 locating above the gas spring lever 22 projects out of the top part of the boss bore 42.

The gas spring lever 22 is generally of a stick shape, and each of the operating end 221 to operate the gas spring lever 22 and a working end 222 to push the projecting and sinking member 211 is of a flat shape generally in parallel to a horizontal surface at a non-operated position. The engaging part 223 to engage the support frame 4 from downward at a position near the working end 222 from the gravity point in a longitudinal direction of the gas spring lever 22 is arranged between the operating end 221 and the working end 222 on the bottom surface of the gas spring lever 22. The engaging part 223 is a hook-shaped projecting part of an “L” character extending in the working end 222 side from the bottom surface of a body of the gas spring lever 22 toward a little further downward, and is integrally formed with the body of the gas spring lever 22.

The gas spring lever mounting part 43 comprising the mounting bore 431, as described based on FIG. 4, is arranged near the top part of the boss bore 42 for the support frame 4. As shown in FIG. 14 and FIG. 15, the gas spring lever 22 is supported with its engaging part 223 inserted into the mounting bore 431 arranged on the support frame 4, and is rotatable in a certain range around the engaging part 223. The operating end 221 extends out toward a side direction of the chair, and the working end 222 locates above the projecting and sinking member 211 of the gas spring 21 in the center part of the chair.

Since the gravity point of the gas spring lever 22 locates nearer the operating end 221 than the engaging part 223, the gas spring lever 22 tries to rotate around the engaging part 223 to locate the operating end 221 at the bottom side just by hooking the engaging part 223 with the mounting bore 431 of the gas spring lever mounting part 43 of the support frame 4, and then the gas spring lever 22 is stabilized at a position where the bottom surface 224 locating rearward of the engaging part 223 makes an abutting contact with the top surface of the gas spring lever mounting part 43. Then with this state kept, it becomes possible to incorporate the support rod 12 into the support frame 4 easily.

Furthermore, in this embodiment, as shown in FIG. 16 and FIG. 17, it is so arranged that the engaging part 223 can not be mounted on or dismounted from the mounting bore 431 unless an angle between the gas spring lever 22 with its working end 222 locating at the bottom side and the horizontal surface becomes more than or equal to a certain degree, and furthermore, as shown in FIG. 15, the working end 222 side of the gas spring lever 22 can be incorporated inside of the boss bore 42 of the support frame 4. Furthermore, after the support rod 12 is incorporated into the boss bore 42 of the support frame 4 it is so arranged that the top part of the support rod 12 interferes with the working end 222 of the gas spring lever 22 so as not to take an angle at which the gas spring lever 22 can be mounted or dismounted. As a result, once the support rod 12 is incorporated, it becomes impossible to dismount the gas spring lever 22 from the support frame 4 without separating the support rod 12 from the support frame 4.

Concretely, as shown in FIG. 15, it is necessary to set an angle between the gas spring lever 22 and the horizontal surface more than or equal to α in order to make it possible to mount or dismount the hook-shaped engaging part 223 arranged on the bottom surface of the gas spring lever 22 on or from the mounting bore 431 of the support frame 4.

The limit angle α at which the gas spring lever 22 is mountable or dismountable is, as shown in FIG. 22, determined uniquely as an angle having a relationship: B×sin α−t1×cos α=t2, wherein t1 is a thickness of the gas spring lever mounting part 43, t2 is a thickness of a distal end of the engaging part 223 of the gas spring lever 22, and B is a width of the mounting bore 431.

If the support rod 12 is dismounted as shown in FIG. 15, it is possible to make the angle more than or equal to α without interfering the working end 222 of the gas spring lever 22 with the other member so that the gas spring lever 22 can be mounted on or dismounted from the support frame 4.

However, in case that the support rod 12 is incorporated into the support frame 4 as shown in FIG. 21, the working eng 222 interferes with the body of the gas spring 21 so that the angle between the gas spring lever 22 and the horizontal surface can take only an angle β even though in a state that the projecting and sinking member 211 of the gas spring 21 is pushed to the maximum position by operating the gas spring lever 22. Since it is so arranged that β becomes sufficiently smaller than α, the once mounted gas spring lever 22 can not be dismounted at this angle.

In addition, the mounting bore 431 of the support frame 4 is, as shown in FIG. 4, in a shape of a general rectangle having a long side orthogonal to a longitudinal direction of the gas spring lever 22 that makes an engagement with the mounting bore 431. The engaging part 223 arranged on the bottom surface of the gas spring lever 22 is so arranged to have a cross section of a general rectangle so as to have an abutting surface tailored to the shape of the mounting bore 43. As a result, the gas spring lever 22 rotates stably in the vertical plane while the gas spring lever 22 is operated so that the gas spring lever 22 will never be deviated from the above of the projecting and sinking member 211.

With this arrangement, if the operating end 221 of the gas spring lever 22 is pulled upward, the working end 222 moves downward with the engaging part 223 as the fulcrum. This movement enables the working end 222 to push the projecting and sinking member 211 of the gas spring 21 so that the height of the seat surface can be adjusted.

As mentioned, the chair of this embodiment comprises the support frame 4 supported by the support rod 12, the back frame 5 that can make an inclining movement relative to the support frame 4, the seat frame 6 that is related to the support frame 4 and the back frame 5 so as to make a movement in conjunction with the back frame 5 toward the direction in the inclining movement of the back frame 5, and the spring case 71 arranged along the seat frame 6 in a state that the proximal point part 716 is supported by the support frame 4 so as to introduce the spring force against the force of the movement of the seat frame 6 and the back frame 5 in conjunction with the support frame 4, and is so arranged that the spring 72 is compressed by the movement of the seat frame 6 relative to the spring case 71, wherein the slide guide parts 66, 67, 68 to make the spring case 71 and the seat frame 6 line-contact in the direction orthogonal to the back and forth direction are arranged between the spring case 71 and the seat frame 6.

With this arrangement, since the area of the part where the spring case 71 makes contact with the seat frame 6 is limited, it is possible to expect to reduce the sliding resistance effectively as a whole. In addition, since the spring case 71 and the seat frame 6 only make a line-contact each other in the direction orthogonal to the direction of the relative movement of the spring case 71 and the seat frame 6, even though the spring case 71 is not arranged in parallel with the seat frame 6, it is possible for the spring case 71 and the seat frame 6 to contact each other so that it does not require a higher accuracy in processing and assembling the spring case 71 and the set frame 6 compared with a case wherein the spring case 71 and the seat frame 6 make a proximal contact.

Especially, in case that the chair of this embodiment is so arranged that the proximal point part 716 of the spring case 71 is supported by the support frame 4 rotatably around the transversal shaft 44 and the base spring bearing 75 is formed on the extending part locating at the distal end side, the movable spring bearing 73 is arranged at the seat frame 6 side to face the base spring bearing 75 and the spring 72 is arranged between the base spring bearing 75 and the movable spring bearing 73, it is likely that the extending part of the spring case 71 swings in the right and left directions due to the force of the spring 72. In order to prevent this, especially the second slide guide part 67 is more effective.

In addition, also in case that the support frame 4 and the spring case 71 can be mounted and dismounted at the assembled angle at least more upright than the used angle, and the cam surface 46 is arranged for the support frame 4 to urge the movable spring bearing 73 toward the direction that the spring 72 is compressed in accordance with the movement of the spring case 71 from the assembled angle to the used angle, the sliding resistance increases because the spring case 71 is pushed against the seat frame 6 and the spring case 71 tends to be disengaged from the seat frame 6. In order to prevent this, especially the first slide guide part 66 is more effective.

In addition, if the void part 65 is formed on a part of the seat frame 6, the spring case 71 is housed in the void 65 at generally the same height as that of the seat frame 6 and the first slide guide part 66 extending in the lateral direction is integrally formed with the seat frame 6 at the position to press the top surface of the spring case 71, it is possible to make the chair compact as a whole.

Furthermore, since the first slide guide part 66 is arranged only at one position along the back and forth direction, it is possible to keep the positional relationship between the spring case 71 and the seat frame 6 appropriate even though the spring case 71 and the seat frame 6 are not arranged strictly in parallel.

In addition, as mentioned above, since the spring case 71 is housed between the right and left walls 612 of the seat frame 6, and the second slide guide part 67 extending in the longitudinal direction is arranged on either the right and left walls 612 of the seat frame 6 or the right and left walls 712 of the spring case 71, it is possible to appropriately support the distal end of the spring case 71 with less resistance in the right and left directions.

Furthermore, since the second slide guide part 67 is arranged only at one position along the back and forth direction, it is possible to keep the positional relationship between the spring case 71 and the seat frame 6 appropriately even though the spring case 71 and the seat frame 6 are not arranged strictly in parallel.

In addition, since the void part 65 opens rearward of the seat frame 6 and the spring case 71 can be mounted on and dismounted from the void part 65 of the seat frame 6 through the opening end 69, it is possible to incorporate the spring case 71 into the seat frame 6 with ease.

Furthermore, since each of the slide guide parts 66, 67, 68 is a projecting part whose distal end is curved to form a convex and is integrally formed with the seat frame 6, it is possible to form the slide guide parts 66, 67, 68 easily and appropriately.

A concrete arrangement of each part is not limited to the above-mentioned embodiment.

For example, in the above-mentioned embodiment the first slide guide part 66, the second slide guide part 67 and the third slide guide part 68 are integrally formed with the seat frame 6 as a convex part to make a line contact with the spring case 71, however, the above-mentioned shape is not indispensable as the shape of the slide guide part 66, 67, 68 as long as the seat frame 6 and the spring case 71 are allowed to make a smooth sliding movement each other while the relative position between the seat frame 6 and the spring case 71 is restricted. The slide guide parts 66, 67, 68 may be of a roller bearing shape wherein a small roller is rotatably mounted on the seat frame 6 as shown in FIG. 23 (a). In addition, the slide guide parts 66, 67, 68 may be a semispherical slider integrally formed with the seat frame 6 as shown in FIG. 23 (b), or may be of a ball bearing type wherein a small ball is rotatably mounted so as to make the seat frame 6 and the spring case 71 point-contact as shown in FIG. 23 (c).

In addition, in the above-mentioned embodiment, the slide guide parts 66, 67, 68 are integrally formed with the seat frame 6, however, since a main function of the slide guide parts is to keep the positional relationship between the seat frame 6 and the spring case 71 appropriately and to allow a smooth sliding movement by decreasing an area where the seat frame 6 and the spring case 71 contact each other, the slide guide parts 66, 67, 68 may be arranged on the spring case 71. In this case, the same effect can be obtained.

EXPLANATION OF THE CODES

-   4 . . . support frame -   5 . . . back frame -   6 . . . seat frame -   7 . . . reactive force mechanism -   44 . . . front transversal shaft -   45 . . . rear transversal shaft -   46 . . . cam surface -   52 . . . middle transversal shaft -   53 . . . frontward facing opening concave part -   62 . . . rotation slide bore -   64 . . . downward facing opening concave part -   66 . . . first slide guide part -   67 . . . second slide guide part -   68 . . . third slide guide part -   71 . . . spring case -   72 . . . compression coil spring -   73 . . . movable spring bearing -   74 . . . bearing member -   75 . . . base spring bearing 

1. A chair comprising a support frame supported by a support rod, a back frame that can make a inclining movement relative to the support frame, a seat frame that is related to the support frame and the back frame so as to make a movement in conjunction with the back frame toward a direction along the inclining movement of the back frame, and a spring case arranged along the seat frame in a state that a proximal point part of the spring case is supported by the support frame so as to introduce a spring force against a force of the interlocking movement of the seat frame and the back frame to the support frame, and is so arranged that a spring is compressed by a movement of the seat frame relative to the spring case, and is characterized by that a slide guide part to make the spring case and the seat frame line-contact in a direction orthogonal to a back and forth direction or point-contact is arranged between the spring case and the seat frame.
 2. The chair described in claim 1, wherein the spring case is so arranged that the proximal point part is rotatably supported by the support frame around a transversal shaft and a base spring bearing is formed on an extending part locating at a distal end side, a movable spring bearing is arranged at the seat frame side to face the base spring bearing and a spring is arranged between the base spring bearing and the movable spring bearing.
 3. The chair described in claim 2, wherein the support frame and the spring case can be mounted and dismounted at an assembled angle at least more upright than an used angle, and a cam surface is arranged for the support frame to urge the movable spring bearing toward a direction that the spring is compressed in accordance with a movement of the spring case from the assembled angle to the used angle.
 4. The chair described in claim 2, wherein a void part is formed on a part of the seat frame, the spring case is housed in the void part at generally the same height as that of the seat frame and a first slide guide part extending in the lateral direction is integrally formed with the seat frame at a position to press the top surface of the spring case.
 5. The chair described in claim 3, wherein a void part is formed on a part of the seat frame, the spring case is housed in the void part at generally the same height as that of the seat frame and a first slide guide part extending in the lateral direction is integrally formed with the seat frame at a position to press the top surface of the spring case.
 6. The chair described in claim 4, wherein the first slide guide part is arranged only at one position along the back and forth direction.
 7. The chair described in claim 5, wherein the first slide guide part is arranged only at one position along the back and forth direction.
 8. The chair described in claim 2, wherein the spring case is housed between the right and left walls of the seat frame, and a second slide guide part extending in the vertical direction is arranged on either the right and left walls of the seat frame or the right and left walls of the spring case facing the right and left walls of the seat frame.
 9. The chair described in claim 3, wherein the spring case is housed between the right and left walls of the seat frame, and a second slide guide part extending in the vertical direction is arranged on either the right and left walls of the seat frame or the right and left walls of the spring case facing the right and left walls of the seat frame.
 10. The chair described in claim 4, wherein the spring case is housed between the right and left walls of the seat frame, and a second slide guide part extending in the vertical direction is arranged on either the right and left walls of the seat frame or the right and left walls of the spring case facing the right and left walls of the seat frame.
 11. The chair described in claim 5, wherein the spring case is housed between the right and left walls of the seat frame, and a second slide guide part extending in the vertical direction is arranged on either the right and left walls of the seat frame or the right and left walls of the spring case facing the right and left walls of the seat frame.
 12. The chair described in claim 6, wherein the spring case is housed between the right and left walls of the seat frame, and a second slide guide part extending in the vertical direction is arranged on either the right and left walls of the seat frame or the right and left walls of the spring case facing the right and left walls of the seat frame.
 13. The chair described in claim 7, wherein the spring case is housed between the right and left walls of the seat frame, and a second slide guide part extending in the vertical direction is arranged on either the right and left walls of the seat frame or the right and left walls of the spring case facing the right and left walls of the seat frame.
 14. The chair described in claim 8, wherein the second slide guide part is arranged only at one position along the back and forth direction.
 15. The chair described in either of claim 4, wherein the void part opens rearward of the seat frame and the spring case can be mounted on and dismounted from the void part of the seat frame from the rearward.
 16. The chair described in claim 1, wherein the slide guide part is a projecting part whose distal end is curved to form a convex and is integrally formed with the spring case or the seat frame. 